With certain manufacturing processes, it is necessary to convey fibrous webs or layers to various stages for further processing or to be combined with other substrates. For example, certain types of desirable composite materials are made by combining pulp fibers with other substrates, including nonwoven spunbonded webs, meltblown webs, scrim materials, and other textile materials. One known technique for combining these materials is by hydraulic entangling. For example, U.S. Pat. No. 4,808,467 discloses a high-strength nonwoven fabric made of a mixture of wood pulp and textile fibers entangled with a continuous filament base web. U.S. Pat. No. 5,389,202 describes a high pulp content composite fabric formed by hydraulically entangling a web of pulp fibers into a continuous filament substrate.
In a typical manufacturing process for hydraulically entangling a layer of fibers into a nonwoven web, the nonwoven material travels in a machine direction on a mesh belt or fabric to a hydraulic entangling station. A dilute suspension containing fibers (pulp, synthetic, or a combination of both) is supplied by a head box and deposited via a sluice onto a forming fabric of a conventional paper-making machine. Water is removed from the fiber suspension to form a uniform layer of fibers on the forming fabric. After being formed, the layer is conveyed in the machine direction and laid onto the nonwoven web. The nonwoven web and overlying fiber layer are conveyed under one or more hydraulic entangling manifolds wherein jets of fluid entangle the fibers into and through the nonwoven substrate to form a composite material. Vacuum slots may be located beneath or downstream of the water jet manifolds to remove excess water from the composite material. After the fluid jet treatment, the composite fabric is conveyed through a non-compressive drying operation, for example a conventional rotary drum through-air drying apparatus.
Regardless of the process, the fiber layer or webs must either have substantial strength so as to maintain their integrity, or be supported by external means or an additional substrate. For example, with a conventional hydro-entangling process, the fiber layer is typically conveyed as a sheet unsupported over at least some distance prior to being combined with the nonwoven substrate. This situation requires the fiber sheet to have substantial strength so as not to loose sheet integrity, particularly in the unsupported locations. In particular, the fiber sheet must have an increased basis weight and include fibers having substantial wet strength characteristics. Processing machine speed is often limited by the fiber sheet characteristics to ensure sheet integrity. However, despite careful attention to the fiber sheet characteristics, it is often the case that the fiber sheet breaks, particularly in the unsupported areas. This results in the loss of valuable production time.
System configurations are known for fully supporting a pulp sheet from a forming section to a dryer section wherein the sheet is supported from below by the former belt, transferred to an intermediate differential speed belt where the sheet is supported from above, and then transferred again to the dryer belt where the sheet is supported from below. It is also known to use this arrangement for transferring a fibrous web from a forming belt to a hydro-entangling belt. However, with such systems, the multiple transfer of the fibrous web or sheet between belts requires complex machinery and can be detrimental in that creases or density variances are created in the sheet or web by the transfer belts.